Project description:A laboratory colony of Phlebotomus perniciosus sand flies was maintained. Sand flies were infected with cultured Leishmania infantum promastigotes in stationary phase. Ten infected sand flies were dissected after 5 days and promastigotes within the gut pooled. The cells were immediately washed in PBS once and lysed in TRIzol reagent (Life Technologies). RNA isolation was completed according to the manufacturer's instructions, obtaining 63ng. RNA-seq libraries were generated using the spliced leader sequence for second strand synthesis (Cuypers et al., 2017; Haydock et al., 2015), thus allowing for specific amplification of sequences from L. infantum promastigotes, thus avoiding contamination with material from the sand fly gut. Single-end sequencing was performed in an Illumina HiSeq2500 instrument and data analysis was conducted using bowtie2, samtools, featureCounts and Geneious. The main findings are: i) substantial differences in differential gene expression between sand fly-derived (sfPro) and cultured (acPro) promastigotes; and ii) over-expression of genes involved in metacyclogenesis in sfPro vs. acPro, including gp63 genes, autophagy genes, etc.
Project description:Leishmania infantum (Kinetoplastida:Trypanosomatidae) is the etiological agent of zoonotic visceral leishmaniasis in the Mediterranean basin. The motile promastigote stage infects the hematophagous sand fly vector host and amastigotes survives and multiplies within phagocytes of the mammalian host. Promastigotes are routinely cultured in liquid undefined media and are considered to mimic the environment within the sand fly gut. We have put this to the test by high-throughput gene expression profiling by shotgun DNA microarrays generated in our laboratory. This has been possible thanks to RNA amplification.
Project description:BackgroundSand flies vector several human pathogens, including Leishmania species, which cause leishmaniases. A leishmaniasis vaccine does not yet exist, so the most common prevention strategies involve personal protection and insecticide spraying. However, insecticides can impact non-target organisms and are becoming less effective because of the evolution of resistance. An alternative control strategy is the attract-and-kill approach, where the vector is lured to a lethal trap, ideally located in oviposition sites that will attract gravid females. Oviposition traps containing attractive microbes have proven successful for the control of some mosquito populations but have not been developed for sand flies. Gravid female sand flies lay their eggs in decomposing organic matter on which the larvae feed and develop. Studies have demonstrated that gravid females are particularly attracted to larval conditioned (containing eggs and larvae) and aged rearing substrates. An isolate-based study has provided some evidence that bacteria play a role in the attraction of sand flies to conditioned substrates. However, the overall bacterial community structure of conditioned and aged substrates and how they change over time has not been investigated.MethodsThe goal of this study was to characterize the bacterial communities of rearing and oviposition substrates that have been shown to vary in attractiveness to gravid sand flies in previous behavioral studies. Using 16S rRNA amplicon sequencing we determined the bacterial composition in fresh, aged, and larval-conditioned substrates at four time points representing the main life-cycle stages of developing sand flies. We compared the diversity, presence, and abundance of taxa across substrate types and time points in order to identify how aging and larval-conditioning impact bacterial community structure.ResultsWe found that the bacterial communities significantly change within and between substrates over time. We also identified bacteria that might be responsible for attraction to conditioned and aged substrates, which could be potential candidates for the development of attract-and-kill strategies for sand flies.ConclusionThis study demonstrated that both aging and larval conditioning induce shifts in the bacterial communities of sand fly oviposition and rearing substrates, which may explain the previously observed preference of gravid female sand flies to substrates containing second/third-instar larvae (conditioned) and substrates aged the same amount of time without larvae (aged).
Project description:The leishmaniases are globally important parasitic diseases for which no human vaccines are currently available. To facilitate vaccine development, we conducted an open label observational study to establish a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis caused by L. major. Between 24th January and 12th August 2022, we exposed 14 (8F, 6M) participants to infected sand flies. The primary objective was to demonstrate effectiveness (attack rate) and safety (absence of CL lesion at 12 months), whereas secondary and exploratory objectives included rate of lesion development, parasite load and analysis of local immune responses using immunohistology and spatial transcriptomics. We estimated a take rate for CL development of 64% (9/14) based on all participants, increasing to 82% (9/11) if only participants with confirmed bites are included. Lesion development was terminated by therapeutic biopsy in 10 participants with confirmed bites. 30% (3/10) had either one (2/10) or two (1/10) lesion recurrences between 4-8 months after biopsy that were treated successfully with cryotherapy. No severe or serious adverse events were recorded, but scarring was evident as expected. All participants were lesion-free at long-term (>12 month) follow up. We provide the first comprehensive map of immune cell distribution and cytokine/chemokine expression in human CL lesions, revealing discrete immune niches. This controlled human infection model offers opportunities for rapid vaccine candidate selection and a greater understanding of immune-mediated protection and pathology.
Project description:Phlebotomine sand flies are vectors of Leishmania that are acquired by the female sand fly during blood feeding on an infected mammal. Leishmania parasites develop exclusively in the gut lumen during their residence in the insect before transmission to a suitable host during the next blood feed. Female phlebotomine sand flies are blood feeding insects but their life style of visiting plants as well as animals, and the propensity for larvae to feed on detritus including animal faeces means that the insect host and parasite are exposed to a range of microorganisms. Thus, the sand fly microbiota may interact with the developing Leishmania population in the gut. The aim of the study was to investigate and identify the bacterial diversity associated with wild adult female Lutzomyia sand flies from different geographical locations in the New World. The bacterial phylotypes recovered from 16S rRNA gene clone libraries obtained from wild caught adult female Lutzomyia sand flies were estimated from direct band sequencing after denaturing gradient gel electrophoresis of bacterial 16 rRNA gene fragments. These results confirm that the Lutzomyia sand flies contain a limited array of bacterial phylotypes across several divisions. Several potential plant-related bacterial sequences were detected including Erwinia sp. and putative Ralstonia sp. from two sand fly species sampled from 3 geographically separated regions in Brazil. Identification of putative human pathogens also demonstrated the potential for sand flies to act as vectors of bacterial pathogens of medical importance in addition to their role in Leishmania transmission.
Project description:A Gram-stain-negative, rod-shaped, non-motile, non-spore-forming, aerobic bacterium, designated type strain SSI9T, was isolated from sand fly (Phlebotomus papatasi Scopoli; Diptera: Psychodidae) rearing substrate and subjected to polyphasic taxonomic analysis. Strain SSI9T contained phosphatidylethanolamine as a major polar lipid, MK-7 as the predominant quinone, and C16 : 1ω6c/C16 : 1ω7c, iso-C15 : 0, iso-C17 : 0 3-OH and C16 : 0 as the major cellular fatty acids. Phylogenetic analysis based on 16S rRNA gene sequences revealed that SSI9T represents a member of the genus Sphingobacterium, of the family Sphingobacteriaceae sharing 96.5-88.0 % sequence similarity with other species of the genus Sphingobacterium. The results of multilocus sequence analysis using the concatenated sequences of the housekeeping genes recA, rplC and groL indicated that SSI9T formed a separate branch in the genus Sphingobacterium. The genome of SSI9T is 5 197 142 bp with a DNA G+C content of 41.8 mol% and encodes 4395 predicted coding sequences, 49 tRNAs, and three complete rRNAs and two partial rRNAs. SSI9T could be distinguished from other species of the genus Sphingobacterium with validly published names by several phenotypic, chemotaxonomic and genomic characteristics. On the basis of the results of this polyphasic taxonomic analysis, the bacterial isolate represents a novel species within the genus Sphingobacterium, for which the name Sphingobacterium phlebotomi sp. nov. is proposed. The type strain is SSI9T (=ATCC TSD-210T=LMG 31664T=NRRL B-65603T).
Project description:Sand flies are the insects responsible for transmitting Leishmania parasites, the causative agents of leishmaniasis in humans. However, the effects of sand fly breeding sites on their biology and ecology remain poorly understood. Herein, we studied how larval nutrition associated with putative breeding sites of the sand fly Lutzomyia longipalpis affects their oviposition, development, microbiome, and susceptibility to Leishmania by rearing L. longipalpis on substrates collected from an endemic area for leishmaniasis in Brazil. The results showed that female L. longipalpis select the oviposition site based on its potential to promote larval maturation and while composting cashew leaf litter hindered the development, larvae reared on chicken feces developed rapidly. Typical gut microbial profiles were found in larvae reared upon cashew leaf litter. Adult females from larvae reared on substrate collected in chicken coops were infected with Leishmania infantum, indicating that they were highly susceptible to the parasite. In conclusion, the larval breeding sites can exert an important role in the epidemiology of leishmaniasis.
Project description:Captive rearing programs (hatcheries) are often used in conservation and management efforts for at-risk salmonid fish populations. However, hatcheries typically rear juveniles in environments that contrast starkly with natural conditions, which may lead to phenotypic and/or genetic changes that adversely affect the performance of juveniles upon their release to the wild. Environmental enrichment has been proposed as a mechanism to improve the efficacy of population restoration efforts from captive-rearing programs: in this study, we examine the influence of environmental enrichment during embryo and yolk-sac larval rearing at the level of the transcriptome in Atlantic salmon (Salmo salar). Full siblings were reared in either a “simple” environment devoid of structure or a “complex” environment enriched with gravel substrate. At the end of endogenous feeding by juveniles, we examined patterns of gene transcription in head tissues using the cGRASP-designed Agilent 4×44K microarray. Significance analysis of microarrays (SAM) indicated that 808 genes were differentially transcribed between rearing environments and a total of 184 gene ontological (GO) terms were over- or under-represented, several of which are associated with mitosis/cell cycle and muscle and heart development. However, there were also pronounced differences among families in gene transcriptional response to rearing environment, with the number of genes significantly differentially transcribed by juveniles in our independent analyses of each family ranging from zero to 3445 (FDR of 5%). Overall, our results suggest that rearing environment enrichment can profoundly change patterns of gene transcription during salmon development, but that the degree of response depends on genetic background.